My first camper, first time winterizing. It's a 2016 White Hawk 28 DSBH. I did everything right except forgot to close the low point drains for the water heater. And it was raining like a monsoon and flooded so I couldn't tell where the antifreeze was going, just knew it was not going where it was supposed to. So to help the next guy here are the steps...
Drain all your tanks and then close your low point drains, make sure you drain your hot water tank too. Make sure your electric and LP gas switches are off.
Close the valves on the water heater and open the bypass valve(it is accessible through a panel under the bottom bunk right next to the water heater
Go under the sink and close the valve that looks like it's going into the holding tank. There are two valves under the sink accessible by removing a thin panel and then you'll see the pump and two valves. One will have a clear hose attached. Put that in your bottle of antifreeze and open the valve. Close the valve next to it, it's labeled the D valve in the manual.
Now turn on the water pump and run the sinks and bathtub, hot and cold, until antifreeze comes out.
Now flush the toilet and fill the bowl a little bit with antifreeze.
Go outside run the shower until antifreeze comes out using both hot and cold knobs. Now turn the water pump off and wipe up the sinks so the pink doesn't stain anything.
Boom, you're done and it's that easy. Took me literally 5 minutes once I figured out the problem with the low point drains being open. I pumped at least 3 gallons out the low point drains because I'm dumb. You can winterize in 1 Gallon if done right